Prepared in cooperation with the U.S. Fish and Wildlife Service Distribution and Movement of Bull Trout in the Upper River Watershed, Nevada Open-File Report 2010-1033 U.S. Department of the Interior U.S. Geological Survey
Distribution and Movement of Bull Trout in the Upper River Watershed, Nevada By M. Brady Allen, Patrick J. Connolly, Matthew G. Mesa, Jodi Charrier, and Chris Dixon Prepared in cooperation with the U.S. Fish and Wildlife Service Open-File Report 2010 1033 U.S. Department of the Interior U.S. Geological Survey
U.S. Department of the Interior KEN SALAZAR, Secretary U.S. Geological Survey Marcia K. McNutt, Director U.S. Geological Survey, Reston, Virginia: 2010 For more information on the USGS the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS. For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprod To order this and other USGS information products, visit http://store.usgs.gov Suggested citation: Allen, M.B., Connolly, P.J., Mesa, M.G., Charrier, Jodi, and Dixon, Chris, 2010, Distribution and movement of bull trout in the upper River watershed, Nevada: U.S. Geological Survey Open-File Report 2010-1033, 80 p. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted material contained within this report.
Contents Abstract... 1 Introduction... 2 Description of Study Site... 2 Study Methods... 3 Fish Collection and Tagging... 3 Habitat Sampling... 4 PIT Tag Interrogation Systems... 5 Data Reconciliation and Analysis... 5 Results of Surveys... 6 West Fork River watershed... 7 East Fork River Watershed... 9 Overall Distribution and Abundance of Bull Trout in Jack Creek... 12 Movements of Bull Trout... 13 Distribution, Growth, and Movement of Bull Trout... 14 General Catch Information and Population Characteristics... 15 Movement of Bull Trout... 17 Conclusions, Summary, and Recommendations... 20 Acknowledgments... 21 References... 21 Appendix table and figures... 64 Figures Figure 1. Map of the East and West Forks of the River, Idaho and Nevada, with the locations of reported fish barriers and passive integrated transponder (PIT) tag interrogations systems installed in 2006 or 2007.... 25 Figure 2. Locations of fish and habitat surveys, fish barriers, and passive integrated transponder (PIT) tag interrogation systems in the West Fork River, Nevada, and its tributaries, 2006 and 2007... 26 Figure 3. Locations of fish and habitat surveys, fish barriers, and passive integrated transponder (PIT) tag interrogation systems in the East Fork River, Nevada, and its tributaries, 2006 and 2007... 27 Figure 4. Length frequency, in 2-mm increments, of all bull trout sampled in the West Fork River, Nevada, in 2006 and 2007... 28 Figure 5. The number of bull trout (BLT) per meter by size class for all habitat units sampled along with altitude (upper graph) and the number of bull trout and redband trout (RBT) per meter by size class in pools only (lower graph) in West Fork River (rkm 21.5 30.2), Nevada, 2006... 29 Figure 6. Number of bull trout (BLT) per meter by size class for all habitat units sampled along with altitude (upper graph) and the number of bull trout and redband trout (RBT) per meter by size class in pools only (lower graph) in West Fork River (rkm 21.7 32.2), Nevada, 2007... 30 Figure 7. Length frequency,in 2-mm increments, of all bull trout sampled in Pine Creek of the West Fork River subbasin, Nevada in 2006 and 2007... 31 Figure 8. Number of bull trout (BLT) per meter by size class for all habitat units sampled along with altitude (upper graph) and the number of bull trout and redband trout (RBT) per meter by size class in pools only (lower graph) in Pine Creek (rkm 0 6.5), Nevada, 2006... 32 iii
Figure 9. Number of bull trout (BLT) per meter by size class for all habitat units sampled along with altitude (upper graph) and the number of bull trout and redband trout (RBT) per meter by size class in pools only (lower graph) in Pine Creek (rkm 0 5.9), Nevada, 2007... 33 Figure 10. Length frequency in 2-mm increments of all bull trout sampled in Jack Creek of the West Fork River, Nevada, in 2006 and 2007... 34 Figure 11. Number of bull trout (BLT) per meter by size class for all habitat units sampled along with altitude (upper graph) and the number of bull trout and redband trout (RBT) per meter by size class in pools only (lower graph) in Jack Creek (rkm 0 4.3), Nevada, 2006... 35 Figure 12. Number of bull trout (BLT) per meter, by size class, for all habitat units sampled along with altitude (upper graph) and the number of bull trout and redband trout (RBT) per meter by size class in pools only (lower graph) in Jack Creek (rkm 0 5.4), Nevada, 2007... 36 Figure 13. Length frequency in 2-mm increments of all bull trout sampled in the East Fork River, Nevada, in 2006 and 2007. Sampling effort is not the same for each year... 37 Figure 14. Number of bull trout (BLT) per meter by size class for all habitat units sampled along with altitude (upper graph) and the number of bull trout and redband trout (RBT) per meter by size class in pools only (lower graph) in East Fork River (rkm 15.6 24.7), Nevada, 2006... 38 Figure 15. Number of bull trout (BLT) per meter by size class for all habitat units sampled along with altitude (upper graph) and the number of bull trout and redband trout (RBT) per meter by size class in pools only (lower graph) in East Fork River (rkm 32.5 35.0), Nevada, 2007... 39 Figure 16. Length frequency in 2-mm increments of all bull trout sampled in Cougar Creek, Nevada, and an unnamed tributary of the East Fork River, Nevada, at rkm 33.5 (measured from the confluence with the West Fork River, Idaho), 2007... 40 Figure 17. Number of bull trout (BLT) per meter by size class for all habitat units sampled along with altitude (upper graph) and the number of bull trout and redband trout (RBT) per meter by size class in pools only (lower graph) in Cougar Creek (rkm 0 3.1), Nevada, 2007... 41 Figure 18. Length frequency in 2-mm increments of all bull trout sampled in Fall Creek of the East Fork River, Nevada, in 2006 and 2007... 42 Figure 19. Number of bull trout (BLT) per meter by size class for all habitat units sampled along with altitude (upper graph) and the number of bull trout and redband trout (RBT) per meter by size class in pools only (lower graph) in Fall Creek (rkm 0 2.0), Nevada, 2006... 43 Figure 20. Number of bull trout (BLT) per meter by size class for all habitat units sampled along with altitude (upper graph) and the number of bull trout and redband trout (RBT) per meter by size class in pools only (lower graph) in Fall Creek (rkm 1.4 3.2), Nevada, 2007.... 44 Figure 21. Length frequency in 2-mm increments of all bull trout sampled in Slide Creek of the East Fork River, Nevada, in 2006 and 2007. Sampling effort is not the same for each year... 45 Figure 22. Number of bull trout (BLT) per meter by size class for all habitat units sampled along with altitude (upper graph) and the number of bull trout and redband trout (RBT) per meter by size class in pools only (lower graph) in Slide Creek (rkm 0 5.5), Nevada, 2006... 46 Figure 23. Number of bull trout (BLT) per meter by size class for all habitat units sampled along with altitude (upper graph) and the number of bull trout and redband trout (RBT) per meter by size class in pools only (lower graph) in Slide Creek (rkm 4.6 7.7), Nevada, 2007... 47 Figure 24. Length frequency in 2-mm increments of all bull trout sampled in Dave Creek of the East Fork River, Nevada, in summer 2006, early summer 2007, and late summer 2007... 48 Figure 25. Number of bull trout (BLT) per meter by size class for all habitat units sampled along with altitude (upper graph) and the number of bull trout and redband trout (RBT) per meter by size class in pools only (lower graph) in Dave Creek (rkm 6.8 11.7), Nevada, 2006... 49 iv
Figure 26. Number of bull trout (BLT) per meter by size class for all habitat units sampled along with altitude (upper graph) and the number of bull trout and redband trout (RBT) per meter by size class in pools only (lower graph) in Dave Creek (rkm 6.8 14.0), Nevada, 2007.... 50 Figure 27. Operational status of interrogation systems during 2007 in the River subbasin, Idaho and Nevada... 51 Figure 28. Number and movement direction of PIT tagged bull trout by month detected at the interrogation site in the East Fork River (EFJ, rkm 4.1), Idaho, and at the East Fork River and West Fork River (Forks, rkm 0.1) interrogation sites, Idaho, during 2007... 52 Figure 29. Streamflow (cfs), temperature, and direction of PIT tagged bull trout movements detected at interrogation sites in West Fork River (rkm 15), Jack Creek (rkm 0.1), and West Fork and Pine Creek confluence (rkm 26), Nevada, 2007... 53 Figure 30. Time of day that PIT tagged bull trout passed any interrogation system in the River subbasin, Idaho and Nevada, in 2006 and 2007... 54 Tables Table 1. Number of bull trout the captured by electrofishing and PIT tagged in the East and West Forks of the River watershed in 2006... 55 Table 2. Number of bull trout captured by electrofishing and PIT tagged in the West Fork River subbasin in 2007... 56 Table 3. Number of bull trout captured by electrofishing and PIT tagged in the East Fork River subbasin in 2007... 57 Table 4. Location, altitude and estimated length of fish and habitat surveys conducted in the River watershed during 2006... 58 Table 5. Location, altitude and estimated length of fish and habitat surveys conducted in the River watershed during 2007... 59 Table 6. Number (n) of bull trout captured, the sampling distance (rkm), the number of bull trout captured with a fork length greater than 200 mm, the number of bull trout with a fork length greater than 250 mm, the minimum (min) fork length, the maximum (max) fork length, and weight of bull trout for each creek sampled in the River watershed, Nevada, in 2006-2007... 60 Table 7. Number (n) of bull trout (BLT) collected, survey length, percent of stream length with bull trout, the percent of habitat units with at least one bull trout, the percent of stream length that was pool-like, and percent of bull trout found in pools in the River watershed in 2006-2007... 61 Table 8. Location and installation date of passive integrated transponder (PIT) tag interrogation units installed in the River watershed in 2006-2007, and the number of bull trout (BLT) interrogated by tagging location in 2006-2007... 62 Table 9. Stream discharge in the River watershed on sampling dates in 2007... 63 v
Conversion Factors and Datums Conversion Factors Multiply By To obtain centimeter (cm) 0.3937 inch (in.) millimeter (mm) 0.03937 inch (in.) meter (m) 3.281 foot (ft) kilometer (km) 0.6214 mile (mi) square kilometer (km 2 ) 0.3861 square mile (mi 2 ) gram (g) 0.03527 ounce, avoirdupois (oz) Temperature in degrees Celsius ( C) may be converted to degrees Fahrenheit ( F) as follows: F=(1.8 C)+32 Temperature in degrees Fahrenheit ( F) may be converted to degrees Celsius ( C) as follows: C=( F-32)/1.8 Datums Horizontal coordinate information is referenced to the World Geodetic System of 1984 (WGS84) datum. Vertical coordinate information is referenced to the WGS84 EGM96 geoid. Altitude, as used in this report, refers to distance above the vertical datum. vi
Distribution and Movement of Bull Trout in the Upper River Watershed, Nevada By M. Brady Allen, Patrick J. Connolly, Matthew G. Mesa, Jodi Charrier, and Chris Dixon Abstract In 2006 and 2007, we surveyed the occurrence of bull trout (Salvelinus confluentus), the relative distributions of bull trout and redband trout (Oncorhynchus mykiss), and stream habitat conditions in the East and West Forks of the River in northeastern Nevada and southern Idaho. We installed passive integrated transponder (PIT) tag interrogation systems at strategic locations within the watershed, and PIT-tagged bull trout were monitored to evaluate individual fish growth, movement, and the connectivity of bull trout between streams. Robust bull trout populations were found in the upper portions of the East Fork River, the West Fork River, and in the Pine, Jack, Dave, and Fall Creeks. Small numbers of bull trout also were found in Slide and Cougar Creeks. Bull trout were numerically dominant in the upper portions of the East Fork River, and in Fall, Dave, Jack, and Pine Creeks, whereas redband trout were numerically dominant throughout the rest of the watershed. The relative abundance of bull trout was notably higher at altitudes above 2,100 m. This study was successful in documenting bull trout population connectivity within the West Fork River, particularly between West Fork River and Pine Creek. Downstream movement of bull trout to the confluence of the East Fork and West Fork River both from Jack Creek (rkm 16.6) in the West Fork River and from Dave Creek (rkm 7.5) in the East Fork River was detected. Although bull trout exhibited some downstream movement during the spring and summer, much of their emigration occurred in the autumn, concurrent with decreasing water temperatures and slightly increasing flows. The bull trout that emigrated were mostly age-2 or older, but some age-1 fish also emigrated. Upstream movement by bull trout was detected less than downstream movement. The overall mean annual growth rate of bull trout in the East Fork and West Fork River was 36 mm. This growth rate is within the range reported in other river systems and is indicative of good habitat conditions. Mark-recapture methods were used to estimate a population of 147 age-1 or older bull trout in the reach of Jack Creek upstream of Jenny Creek. 1
Introduction The River population of bull trout (Salvelinus confluentus) was listed as threatened under the Endangered Species Act on April 8, 1999 (64 Federal Register 17110). Bull trout within the River are presumably limited to a single core area within the upper watershed, which comprises six local populations: (1) East Fork River (including the East Fork headwaters, Cougar Creek, and Fall Creek); (2) West Fork River (including Sawmill Creek); (3) Dave Creek; (4) Jack Creek; (5) Pine Creek; and (6) Slide Creek (U.S. Fish and Wildlife Service, 2004). Bull trout populations in these areas are thought to be mostly local, with few migratory (fluvial) fish present. In 2004, the River Bull Trout Recovery Team estimated that fewer than 500 bull trout, with 50 125 reproductively mature fish, were present within the core area (U.S. Fish and Wildlife Service, 2004). Several factors are suspected to have limited the River bull trout population historically, including livestock grazing, elevated water temperatures, road construction and maintenance, mining, and hatchery supplementation of rainbow trout (Oncorhynchus mykiss) (U.S. Fish and Wildlife Service, 2004). Stocking of hatchery rainbow trout was suspended in 1998. In 2006, the U.S. Fish and Wildlife Service (USFWS) formed a cooperative agreement with the U.S. Geological Survey s (USGS) Columbia River Research Laboratory (CRRL) for USGS to collect information on the life history, movements, abundance, and distribution of bull trout in the upper River basin. This information was needed to assist managers in making informed decisions regarding bull trout recovery. The objectives of the resulting study were to: (1) monitor the movements, distribution, and growth of bull trout in selected tributaries of the River basin; (2) estimate the abundance of selected local bull trout populations; (3) conduct habitat surveys and assess habitat conditions; and (4) use the data collected as a baseline to develop a cost-effective monitoring strategy to assess population trends over time until recovery is achieved. The USGS investigators regularly coordinated with the River Bull Trout Recovery Team, which comprises staff members from the Idaho Department of Environmental Quality, Bureau of Land Management (BLM), Nevada Department of Wildlife (NDOW), the U.S. Forest Service (USFS), USFWS, and Idaho Department of Fish and Game. This report summarizes study findings from 2006 and 2007. Description of Study Site The headwaters of the River are in the Mountains of northeastern Nevada. The watershed is characterized by an elevated volcanic plateau that gradually slopes northward to the Snake River Plain, which drains approximately 1,264 km 2 (488 mi 2 ; U.S. Fish and Wildlife Service, 2004). The upper watershed has a mountainous north-south crest with eight peaks greater than 3,050 m (10,000 ft) high. The East Fork and West Fork of the River flow northward for about 36 and 32 km, respectively, and merge about 6.4 km downstream of the Idaho-Nevada border. This confluence of the two forks was the downstream extent of our study area (fig. 1). The mainstem River continues another 45 km northwest and eventually empties into the Bruneau River in Idaho. Riparian vegetation in the watershed consists of juniper (Juniperus spp.), black cottonwood (Populus balsamifera), subalpine fir (Abies lasiocarpa), aspen (Populus tremuloides), and various forbs, grasses, and sedges (U.S. Fish and Wildlife Service, 2004). The Mountains have a subalpine climate and receive substantial amounts of precipitation, primarily in the form of snow, which is the major source of 2
water for streams in the basin. Additional precipitation falls as rain during thunderstorms. Runoff follows the natural hydrograph, with high spring and early summer flows that diminish in the late summer but increase slightly during fall and winter. The only streamgaging station in the watershed is within our study area on the West Fork River downstream of, Nevada (USGS station number 13162225). Study Methods Fish Collection and Tagging We sampled all streams within the River basin known to contain bull trout as identified by the River Bull Trout Recovery Team. These included parts of the East Fork and West Fork River, and Cougar, Fall, Slide, Dave, Jack, and Pine Creeks (figs. 2 and 3; tables 1, 2, and 3). In an attempt to find other streams containing bull trout, we conducted exploratory sampling in selected reaches of Deer, Buck, Sawmill, and God s Pocket Creeks, and on an unnamed tributary of the East Fork River. Successive samples were collected in an upstream direction with the goal of reaching the end of fish distribution while tagging as many bull trout as possible of the appropriate size. In several streams, some sections were skipped in an effort to sample reaches with higher bull trout densities, which maximized the returns of the effort given the time allotted. The upper end of fish distribution was confirmed by electrofishing upstream of the likely barrier for approximately 100 m where practicable. Bull trout samples were collected using a Smith-Root model 15-B backpack electrofisher equipped with one small probe and one rat tail electrode. Each stream reach was electrofished in a single upstream pass and all habitats likely to contain bull trout were sampled. All observed bull trout were captured. Redband trout were not captured, but were enumerated and generally classified as being less than 80 mm, 80 to 150 mm, or larger than 150 mm in pools only. The occurrence of redband trout in pools was recorded to indicate their general abundance without overly slowing the progress of the sampling crew that would have resulted if redband trout had been counted and classified in the much longer non-pool sections as well. The general abundance of other fish species was noted as rare, present, or highly abundant. All captured bull trout were anesthetized with a 50-mg/L solution of tricaine methanesulfonate (MS-222), measured fork length to the nearest millimeter, weighed to the nearest 0.1 g, and inspected for reproductive status and external signs of disease or injury. We tagged bull trout using full-duplex SGL model passive integrated transponder (PIT) tags (manufactured by Biomark, Inc., Boise, Idaho) that were 12 mm in length and operated at a frequency of 134.2 khz. Fish less than 70 mm were considered too small to tag. In fish between 70 and 120 mm long, tags were injected into the peritoneal cavity. Fish greater than 120 mm were tagged in the dorsal sinus to minimize the potential for shedding of tags during spawning. A sample of caudal fin tissue was removed from most bull trout, placed in a pre-labeled vial containing 2 ml of 100% non-denatured ethanol, and sent to the USFWS s Abernathy Fish Technology Center (Longview, Wash.) for genetic analysis as part of a separate, but coordinated study (De Haan and others, 2007). Where bull trout were locally abundant, a genetic sample was taken from a subset of bull trout; otherwise a genetic sample was collected from each fish. After they recovered from the effects of tagging, fish were released in the location of capture. 3
In 2007, we conducted a Petersen mark-recapture population estimate for bull trout in Jack Creek. To facilitate repeatability, Jack Creek was selected because of ease of access and the known presence of a bull trout population. The population was estimated in two sections of Jack Creek: from the confluence with West Fork River upstream to the confluence of Jenny Creek (rkm 1.8); and upstream of Jenny Creek to the end of fish distribution (rkm 5.4). Three block nets and a picket weir were placed consecutively at the downstream end of each section to ensure a closed population. We electrofished the sections in one slow, methodical upstream pass, each within 1 day. In both the 3.6 km section upstream of Jenny Creek and the 1.8 km section downstream, three people started at the block nets on the downstream end, and three others started at the mid point. Only bull trout longer than 80 mm (age-1 or older) were included in the estimate. We tagged all captured bull trout, and the recapture effort occurred 24-30 h later. Habitat Sampling Along with electrofishing, we conducted habitat surveys using the classification system described by Bisson and others (2006), which is a modification of an earlier hierarchical subdivision of channel units by Hawkins and others (1993). Using this system, we classified habitat units into pools and non-pools. We conducted daily visual distance calibrations for personnel with a measuring tape. On the basis of these visual estimates, we recorded the length and width of each habitat unit. We also measured maximum and mean water depths, and visually estimated the percent total instream and overhead cover by cover type (for example, large and small wood, substrate, and undercut bank), and percent riparian shade provided by trees and shrubs. Global positioning system (GPS) location coordinates and altitudes were recorded at the beginning and end of the survey each day. Stream temperature data were collected with a handheld thermometer at all electrofishing sites in the morning, at mid-day, and in the afternoon (appendix table A1) to ensure that temperatures were appropriate for electrofishing or PIT tagging. Because of the high variability of water temperatures measured with handheld thermometers, owing to the time of year, time of day, weather, and proximity to springs, among other factors, this temperature information was not used in the analysis, but is provided in the appendix. Stream temperatures also were recorded by the BLM via a network of automated thermographs placed at various sites throughout the East and West Forks Rivers; this temperature information was used in the analysis. Seven streamflow monitoring stations were established near the PIT tag interrogation system (PTIS) sites for the purposes of this study. Stream discharge measurements were made at each of these stations three times in August 2007 to assess tributary contributions to overall flow. Following the protocol of Bain and Stevenson (1999), we anchored a measuring tape perpendicular to streamflow and recorded the distance to the left and right wetted edge. We measured water depth and velocity with a Marsh-McBirney model 2000 flow meter at a minimum of 10 (although usually at about 20) intervals along the measuring tape. Because water depths were always less than 1 m, water velocities were measured at 60% of the depth at each interval. 4
PIT Tag Interrogation Systems On September 15, 2006, we installed instream PTISs at three locations: at the mouth of Jack Creek; in West Fork River about 2.4 km downstream of Jack Creek; and in East Fork River near the town of, Idaho (fig. 1). At Jack Creek, one PIT tag transceiver (model FS2001F-ISO, Digital Angel, St. Paul, MN, USA) with a single custom antenna was installed. This site was powered by one 12-volt battery, which was trickle-charged by a solar panel. On the West Fork River, we installed two stream-width, pass-by antennas connected to a multiplexing transceiver (model FS1001M (MUX), Digital Angel, St. Paul, Minn., USA). The transceiver was powered by four 12-volt batteries, which were tricklecharged by two solar panels. The design of the PTIS in the East Fork River was similar to that in the West Fork River, but with two arrays of two pass-through antennas installed. The multiple-antenna design system, which was used and is described by Connolly and others (2005), was expected to provide high detection efficiencies; however, the systems installed for this project had two arrays instead of three, which would reduce the detection efficiencies as well as the ability to calculate them (Connolly and others, 2008). Data from the PTISs were downloaded and the batteries were changed once a week from September through December 2006, after which the equipment was removed for the winter. In 2007, six PTISs were installed, three at the pre-established (in 2006) sites and three at new sites. On April 28, 2007, the three PTISs described above were reinstalled (fig. 1). In Dave Creek, on May 23, 2007, at about rkm 0.4, a single-antenna PTIS was installed similar to the one in Jack Creek. In the West Fork River, a MUX-style PTIS was installed on July 16, 2007, at the confluence of Pine Creek (rkm 26.2), with two stream-width antennas in Pine Creek and two in the West Fork River just downstream of the confluence. At the confluence of the East Fork and West Fork River ( the Forks ), another PTIS was installed on July 17, 2007. This system was comprised of two stream-width antennas in both the East Fork and West Fork River. To prevent damage to the PTIS equipment during winter, the units were removed from all sites on December 19, 2007. In general, the PTISs were strategically placed to investigate the potential linkage between local populations of fish throughout the watershed. In both years, the systems were tested with a test tag when battery exchanges or data downloading occurred. Data Reconciliation and Analysis Detections of PIT tagged fish were merged with tagging data. We used independent reconciliation of PIT tag records by two biologists to classify movements as upstream, downstream, or of unknown direction. The time and location of tagging and other interrogation events were used to determine the direction of fish movements. If multiple interrogation events of the same fish occurred within 2 days, they were considered to be one movement event. Directional fish movement events were accepted when there was consensus on the direction of movement by the two biologists. If discrepancies in assigning direction could not be reconciled, the movement was recorded as an unknown direction. The operational run times for the systems were determined using the buffer data (see below) and the field log notebooks of the PTIS units. The buffer data provided records of the dates and times that each interrogation system was running. Additional information was obtained by reviewing the field notes, which were recorded during downloading. 5
Recaptured bull trout were used to calculate information on movement and growth rates. Annual growth rates were calculated for all recaptured fish with more than 320 days between tagging and recapture. Because the number of days between tagging and recapture varied among individuals and between fish in different streams, the annual growth rate was standardized to a full year by dividing the change in length by the fraction of the year between capture and recapture. We conducted length frequency analysis to determine fish age at length for age-0 to age-2 bull trout. The length frequency histograms exhibit distinct modes of the first few age classes, which can provide insight into annual growth rates. The growth rate from length frequency analysis was validated with growth rates calculated via recaptured PIT tagged fish. For our mark recapture study, we estimated the number of bull trout in two sections of Jack Creek as follows: N = [(M + 1)*(C + 1)/ R + 1] 1, (1) where M = number of fish marked on the first sample, C = number of fish captured in the second sample, and R = number of fish with a mark captured in the second sample. The confidence interval for each estimate was calculated using a binomial distribution when R/C was greater than 0.10 (Seber, 1982). To estimate discharge at our streamflow monitoring stations, flow was computed by summing the flows of intervals, where the flow at each interval was calculated using the equation: Q n d n b n 1 b 2 n 1 vn, (2) where Q = discharge at interval n, d = water depth at interval n, b = distance along the tape n n measure from the left wetted edge to point n, and = mean velocity in interval n. Results of Surveys From July 19 to October 4, 2006, we sampled a total of 39.9 km of stream channel in reaches of East Fork and West Fork River, and in Fall, Slide, Dave, Jack, and Pine Creeks (figs. 2 and 3). A total of 349 bull trout were captured, of which 322 were PIT tagged and 237 were fin clipped for genetic analysis by the USFWS (table 1). The majority (84%) of fish were PIT tagged in Dave Creek, West Fork River, and Jack Creek. We collected only a few age-0 bull trout three in upper Jack Creek, two in upper West Fork River, and one in Pine Creek. Sampling ended because of observed spawning activity by fish in Dave (August 6), Slide (August 22), and Jack (September 11) Creeks. We observed no direct bull trout mortalities during sampling in 2006. From June 13 to September 14, 2007, we sampled 24.9 km of stream channel in the West Fork River and its tributaries, and 18 km of stream channel in the East Fork River and its tributaries (tables 2 and 3). The total lengths of stream sampled and latitude and longitude of the start and end points are shown in tables 4 and 5. In 2007, 1,353 bull trout were captured, of which 1,214 were PIT tagged, and 569 were fin clipped for genetic analysis (tables 2 and 3). The majority (88%) of bull trout were PIT tagged in upper East Fork River, upper West Fork River, and Dave, Pine, and Jack Creeks. We collected substantially more age-0 fish in 2007 than in 2006 four fish in upper Dave Creek, 41 fish in Jack Creek, v n n 6
36 fish in Pine Creek, and a single 28-mm bull trout collected on June 22, 2007, in the upper West Fork River. Three fish died as a consequence of electrofishing (direct mortality) in 2007, which was 0.2% of the total number of bull trout handled. In addition to bull trout, redband trout, sculpin (Cottus spp.), and mountain whitefish (Prosopium williamsoni) were commonly encountered during sampling. In 2006, in the lower East Fork River just upstream of, we also encountered dace (Rhinichthys spp.), bridgelip sucker (Catostomus columbianus), and redside shiner (Richardsonius balteatus). We found no evidence of disease or introgression (vermiculation and pigment on the dorsal fin) with brook trout (Salvelinus fontinalis) in any of the bull trout we captured. West Fork River watershed West Fork River. In 2006, one bull trout was captured near the West Fork River antenna site (rkm 14.5 15.5), and 96 fish were captured between rkm 22.0 30.0 (table 1). Sampling was stopped 1.3 km downstream of the end of fish distribution (as determined in 2007) due to time constraints. In 2007, sampling started at the first bridge upstream of the town of (rkm 21.7) and ended at rkm 32.2, 100 m upstream of a 1.3-m barrier falls, which was the uppermost point of fish distribution, as indicated by our sampling. We also sampled about a 100-m long reach of Sawmill Creek (which contributed 25% of the total West Fork River flow) and captured one redband trout and no bull trout. Several temporary, naturally formed low-flow fish barriers (substrate and wood) were present in West Fork River in 2007, with the most downstream barrier about 1.5 km upstream of the confluence with Pine Creek. In 2007, 272 bull trout were captured between rkm 21.7 and 32.2 (table 2, fig. 2). For both years, the minimum fork length was 23 mm, and the maximum was 330 mm (table 6). Most of the bull trout were age-1 and age-2, with relatively few fish longer than 200 mm (11% of our catch in 2006, 7% in 2007; table 6, fig. 4). In 2007, we recaptured six bull trout that were originally PIT tagged in July and August 2006. The mean annual growth rate of these fish was 32 mm (range = 8-39 mm; SD = 4.8; fig. 4). The length of these fish at tagging ranged from 90 to 185 mm. Using length-frequency analysis, we estimated age-1 bull trout to be between 83 and 115 mm and age-2 fish to be longer than 120 mm in late July and early August 2006. In June 2007, age-1 bull trout were between 70 and 115 mm, and age-2 fish were from 120 to about 160 mm. In both years, bull trout were found primarily at altitudes above 2,100 m and in greater abundance at increasingly greater altitudes (figs. 5 and 6). Redband trout were found throughout the area we sampled, but with reduced abundances as altitude increased. In 2006, bull trout longer than 200 mm were more common in the lower altitude reaches than in the higher reaches, but they were more evenly distributed in 2007. We sampled earlier in 2007 (June July) than in 2006 (July September), which could account for the differences in fish distribution. We sampled earlier in the year in 2007 because we encountered spawning activity during our sampling in 2006. A single age-0 bull trout was collected in the West Fork River in each year (figs. 4, 5, and 6). These fish were collected in the uppermost reaches, at altitudes greater than 2,100 m (figs. 5 and 6). 7
Of the 12,586 m of stream channel surveyed in 2006, 21% of the habitat units contained at least one bull trout. In 2006, 20% of the bull trout were found in pools and 16% of the habitat length we surveyed was pool habitat (table 7). In 2007, 50% of the habitat units surveyed contained at least one bull trout. Fifteen percent of these fish were found in pools and 12% of the habitat length we surveyed was pool habitat (table 7). In 2007, the upper end of our sampling was located higher in the basin (fig. 2), which may account for the greater number of habitat units containing bull trout. Pine Creek. Sampling in Pine Creek in both years began at the confluence of Pine Creek and West Fork River (fig. 2). In July 2006, about 5.5 km of stream habitat were sampled, with the exception of about 1.8 km of middle Pine Creek. In August 2007, sampling was continuous over 5.9 km of stream, but stopped about 200 m downstream of the end of fish distribution (as assessed by visual survey). In 2006, 27 bull trout were captured and 25 were PIT tagged (table 1). In 2007, 430 bull trout were captured, of which 380 were PIT tagged (table 2). Fish lengths ranged from 39 to 387 mm (table 6) and most were age-1, as determined from length frequencies (fig. 7). In both years, we captured only a few bull trout longer than 200 mm (table 6, fig. 7). In 2007, we recaptured two bull trout that were originally PIT tagged in July 2006. The lengths of these fish at tagging were 108 and 162 mm and their annual growth rates were 57 and 35 mm (adjusted to 1 year), respectively, with 397 days between tagging and recapture (fig. 7). In 2006, one age-0 (39 mm) bull trout was captured and age-1 fish were between 100 and 130 mm, as determined from length frequency analysis (fig. 7). Age-0 bull trout captured in August 2007 ranged between 55 and 68 mm, and age-1 fish were from 99 to 155 mm in length (fig. 7). In both years, bull trout were found mostly above 2,100 m altitude and in greater numbers and at higher abundances as altitude increased (figs. 8 and 9). Redband trout were found throughout the reaches sampled, but with reduced abundances in the highest altitudes. The middle reach of Pine Creek, which we did not sample in 2006, had the highest abundances of bull trout in 2007, with bull trout >200 mm long common. In 2006, only one age-0 bull trout was collected, whereas in 2007, several age-0 fish were captured in the reaches above 2,187 m altitude; figs. 7, 8, and 9). The highest altitude reaches had age-0 bull trout and redband trout present and relatively high abundances of bull trout overall. Only 14% of the habitat units surveyed in 2006 contained bull trout, but 83% of habitat units contained at least one bull trout in 2007. This discrepancy probably was due to more extensive sampling in the middle and upper reaches of Pine Creek in 2007. In 2007, about 10% of the bull trout were found in pools, though only 9% of the stream length sampled was pool habitat (table 7). Jack Creek. In both years, sampling in Jack Creek began near the confluence with the West Fork River (fig. 2). In 2006, sampling began 20 m upstream of the PTIS (rkm 0.1) and continued to about rkm 4.3. We stopped sampling near this area because of fish spawning activity. On September 11, 2006, two pair of post-spawn bull trout were collected and several redds were observed. In 2007, our sampling began at the mouth of Jack Creek, continued to rkm 5.9, and included a mark-recapture population estimate presented below. This sampling extended about 100 m past the uppermost distribution of fish, which appears to end at a small waterfall with a 60 m bedrock slide downstream. On September 11, 2007, 0.8 km of stream was sampled above the presumed end of fish distribution, and no fish were observed. In early September 2006, 66 of the 70 bull trout captured were PIT tagged (table 1). In early August 2007, 101 of the 146 bull trout captured were PIT tagged (table 2, fig. 2). The minimum fork length was 61 mm in 8
2006 and 42 mm in 2007, and the maximum fork length was 310 and 283 mm (table 6), respectively. Most of the bull trout were age-1, with small percentages larger than 200 mm (11% in 2006, 10% in 2007; table 6, fig. 10). We recaptured 10 bull trout in August 2007 that were originally PIT tagged in September 2006. The length of these fish at tagging ranged from 125 to 235 mm. The mean annual growth rate of these fish was 34 mm (range = 21 44 mm; SD = 4.8; fig. 10). Using length-frequency analysis, we determined that age-0 fish were less than 69 mm in early September 2006, age-1 bull trout were 115 142 mm, and age-2 bull trout were larger than 145 mm (fig. 10). In August 2007, age-0 bull trout were 42 62 mm, age-1 fish were 980 140 mm, and age-2 fish were 145 190 mm (fig. 10). Consistent with findings in other streams in the upper River watershed, bull trout generally were found in greater numbers and at higher abundances at altitudes above 2,100 m and in greater numbers and at higher abundances as altitude increased (figs. 11 and 12). Redband trout were found in high abundances in lower Jack Creek below about 2,100 m altitude. Bull trout presence extended 500 600 m upstream of the last observed redband trout in both years in Jack Creek. In 2006, bull trout longer than 200 mm were found in the middle and upper portions of Jack Creek (fig. 11), but in 2007, fish of this size were found only in one area, at rkm 4.0 (fig. 12). In 2006, age-0 bull trout were found only at altitudes greater than 2,000 m. In 2007, however, age-0 bull trout were found about 0.5 km from the confluence, at about rkm 2.2, and also at rkm 4.2 near the high abundance of age-1 or older bull trout. Of the 5.2 km of Jack Creek surveyed in 2006, 29% of the habitat units contained at least one bull trout. Although only 10% of the stream length surveyed was pool habitat (table 7), 44% of the bull trout captured were in pools. In 2007, we surveyed 5.4 km of stream and 45% of the habitat units contained at least one bull trout. We captured 39% of the bull trout in pools, while only 8% of the length of stream was pool habitat (table 7). Deer Creek. On September 10, 2007, we sampled Deer Creek from about rkm 6.9 to 9.4. Several small redband trout were observed, but not counted. No bull trout were observed. The riparian vegetation in the reach sampled was very sparse. The stream had a mean depth of 5 cm and very limited pool habitat. Buck Creek. We sampled two short reaches of Buck Creek (from about rkm 3.6 3.8 and rkm 12.7 13.1) on September 14, 2007. The habitat in Buck Creek was similar to that in Deer Creek. It was about 7 cm deep, lacked defined pools, and had sparse riparian vegetation. In general, the stream had very low velocity, heavy siltation, and high turbidity. Redband trout were abundant; however, no bull trout were observed. East Fork River Watershed East Fork River. In 2006, we sampled near the East Fork River antenna site (rkm 4.1 4.9) on October 3 and in the wilderness area upstream of the East Fork River/Slide Creek confluence (rkm 15.6) from August 17 19 (fig. 3). No bull trout were captured near the antenna site, but 13 were captured between rkm 16.6 and 24.7 (table 1). Sampling stopped at rkm 24.7 due to time constraints. We sampled the East Fork River (rkm 32.5 35.0) from July 12 14, 2007, and captured 323 bull trout, of which 312 were PIT tagged (table 3, fig. 3). We also sampled 250 m of an unnamed tributary at about rkm 33.5. Redband trout were absent, but 13 bull trout, ranging from 130 to 238 mm, were captured in this tributary (table 3, fig. 16). We encountered a 2.5-m-high falls with no plunge pool 250 m upstream of the mouth of the unnamed tributary. We sampled an additional 50-m reach upstream 9
of this barrier and found no fish. On the mainstem East Fork River below the confluence of Slide Creek, we recaptured one bull trout on July 17, 2007, that was originally tagged in Fall Creek in August 2006 (table 3, fig. 3). We stopped sampling in 2007 at approximately rkm 35.0 due to time constraints. Visual surveys indicated that fish were likely present for at least another 0.5 km upstream of our end point based on habitat conditions and water quantity. However, this survey was brief and no fish were directly observed. The maximum size of fish tended to be larger in the upper East Fork River than anywhere else we sampled. In 2006, bull trout ranged in length from 135 to 260 mm (table 6) and in 2007 from 78 to 400 mm (table 6). Most of the fish we captured were age-3 or older, with a relatively high proportion of fish longer than 200 mm (38% in 2006; 19% in 2007) (table 6, fig. 13). From length-frequency analysis, we determined that age-1 bull trout were between 78 to 100 mm, age-2 bull trout were between 107 and 143 mm, and age-3 bull trout were 143 mm and longer in mid-july 2007 (fig. 13). The sample size was too small in 2006 to determine age classes. No age-0 bull trout were observed in the East Fork River during 2006 or 2007. In 2006, bull trout were uncommon but increased in abundance at altitudes above 2,100 m near the upstream end of our survey (fig. 14). Redband trout were abundant throughout the area sampled in 2006. In 2007, bull trout were present at the downstream end of our sampling (fig. 15), were numerically dominant at about 2,290 m altitude, and were the only salmonid present above 2,320 m altitude. Bull trout abundance decreased upstream of the East Fork River confluence with an unnamed tributary and spring at rkm 33.5. In this area, stream depths were very shallow and the stream contained no surface flow for about 100 m. Surface flow and high numbers of bull trout were present upstream of the no-flow section and the channel substrate primarily was bedrock. On July 14, 2007, the last day of sampling the upper East Fork River, bull trout were the only salmonid present and were relatively abundant. We speculate that high abundance of bull trout continued at least another 0.5 km upstream as no barriers were present. In 2007, we recaptured a large bull trout (400 mm) at our lowermost sampling site in the East Fork River (fig. 3). This same fish was originally tagged in Fall Creek (see appendix, fig. A49) and had grown 40 mm and nearly doubled its weight in 331 days (440.6 to 767.2 g, table 6). We recaptured no other PIT tagged fish in 2006 from the East Fork River. We surveyed 8 km of the East Fork River in 2006 and only 5% of the habitat units contained bull trout. We found 25% of the bull trout in pools, while 19% of the length sampled was pool habitat (table 7). In 2007, the survey in the East Fork River covered a higher altitude reach except for a short 0.4-km reach at the East Fork River/ Slide Creek confluence (fig. 3) and 52% of the habitat units sampled had bull trout (table 7). Nineteen percent of the bull trout we captured were in pools, while 13% of the stream length sampled was pool habitat. Cougar Creek. We sampled Cougar Creek on July 11 12, 2007, starting at the confluence with the East Fork River and continuing upstream 0.7 km; no bull trout were observed in this reach (table 3 and fig. 3). Several temporary, low-flow fish barriers (mostly substrate and wood) were present. From about rkm 1.2 1.5, we captured one bull trout that was 138 mm long. From rkm 1.8 to the limit of fish presence at rkm 3.1, we caught six bull trout, ranging in length from 180 to 340 mm (table 6, figs. 16 and 17). Here, the substrate was bedrock and the stream had a steep gradient above 2,100 m altitude. Although there were several cascading waterfalls and slides in this section, redband trout were relatively abundant. The end of 10
fish distribution was a 2.5-m-high falls; we electrofished upstream of these falls an additional 100 m, but no fish were observed. Cougar Creek was not sampled in 2006. Only 4% of the habitat units contained bull trout in Cougar Creek, and five of the seven bull trout we caught were in pools (table 7). Fall Creek. We sampled Fall Creek on August 20, 2006, starting at the confluence with the East Fork River and continuing upstream for about 2.0 km (fig. 3). On July 15, 2007, we sampled from rkm 1.4 to rkm 3.4, but did not find any fish upstream of rkm 3.2 (fig. 3). In 2006, we captured and PIT tagged nine bull trout (table 1). In 2007, 30 bull trout were captured and PIT tagged (table 3). The combined range of lengths of fish from both years was 79 360 mm (table 6). Most of the bull trout in 2007 were age-1, with only a few age-2 fish present (fig. 18). The sample size of fish in 2006 was too small for age determinations. One bull trout longer than 200 mm that was PIT tagged in 2006 was subsequently recaptured in 2007 in the mainstem East Fork River (rkm 23.5) near the confluence with Slide Creek, about 2.5 km from the tagging site. In 2006, bull trout were uncommon from the confluence with the East Fork River to about 1.0 km upstream (fig. 19). In 2007, bull trout were found with increasing frequency and abundance in the higher altitudes sampled (fig. 20). Four bull trout longer than 200 mm were caught near the end of fish distribution (fig. 20). All size classes of redband trout were found throughout the length of stream sampled in 2006. In 2007, redband trout abundance decreased in the upper reaches of Fall Creek, and bull trout were the only salmonid present in the final 130 m of stream below a barrier waterfall. Of the 2.0 km of Fall Creek surveyed in 2006, only 8% of the habitat units contained bull trout. Twenty-two percent of the catch was from pools, and 14% of the stream length was pool habitat. Of the 1.8 km of stream sampled in 2007, 28% of the habitat units contained at least one bull trout, with 20% of the fish found in pools. Only 9% of the stream length sampled was pool habitat (table 7). Slide Creek. On August 21, 2006, we sampled Slide Creek from its confluence with the East Fork River upstream to rkm 5.5, where we observed spawning bull trout. We did not sample two small sections in 2006, one from rkm 2.9 to rkm 3.2 and another from rkm 4.6 to rkm 5.4 (table 1, fig. 3). On July 16, 2007, we sampled the creek from rkm 4.6 to rkm 7.7 (table 3 and fig. 3). In 2006, four bull trout were captured and PIT tagged (table 1) and in 2007, only three fish were captured and PIT tagged (table 3). The length of bull trout ranged from 189 to 300 mm in 2006 and from 95 to 220 mm in 2007 (table 6 and fig. 21). On August 22, 2006, we observed two gravid bull trout (300 and 190 mm) and another spawning pair and therefore stopped sampling. In 2006, all four of the bull trout were captured at an altitude above 2,100 m (fig. 22). In 2007, two of the bull trout we caught were likely age-1 fish, on the basis of estimates of size at age from other fish in the East Fork River (fig. 21). The lengths of the few bull trout caught in 2007 varied widely, and the largest fish (220 mm) was caught very high in the watershed (fig. 23). No bull trout were caught in pools in either year (table 7, figs. 22 and 23). All size classes of redband trout were found throughout Slide Creek in 2006 and 2007. Sampling efficiency generally was less in Slide Creek relative to that in other streams due to narrow stream width and thick riparian vegetation. Dave Creek. In August 2006, we collected samples between rkm 6.8 and rkm 11.7 on Dave Creek and PIT tagged 111 of the 129 bull trout collected (table 1, fig. 3). We stopped sampling on August 6 because we encountered one sexually mature male bull trout and two bull trout paired together over spawning gravel. From June 28 through July 2, 2007, sampling started 11